1. Field of the Invention
The present invention relates to an information repeater system, and is suitably applied, for example, to an information repeater system for receiving a digital satellite broadcasting wave formed by multiplexing the programs of plural channels, extracting an arbitrary channel, and then distributing it to the. desired channel of a cable broadcasting system.
2. Description of the Related Art
Heretofore, there has been a compression coding method called MPEG2 (moving picture experts group phase 2) as a method for reducing the amount of information such as video and audio or the like. A DVB (digital video broadcasting) system has been provided as a digital broadcasting system for compressively coding video and audio broadcasting data using the above compression coding method and broadcasting programs using terrestrial waves or satellite waves. In this broadcasting system, broadcasting data compressively coded by the MPEG2 system is packetized in each prescribed block, and thus obtained packet train is transmitted (hereinafter, the packet is referred to as TS (transport stream) packet and a data stream formed of a train of the above TS packet is referred to as transport stream). Furthermore, in the digital broadcasting system, thus packetized broadcasting data of plural program channels are multiplexed. Thereby, plural program channels can be broadcasted by a single line.
In this connection, a program channel is one of broadcasting services. One formed by multiplexing plural program channels is referred to as single transmission channel. The above single transmission channel is relayed by the corresponding single transponder of a communication satellite. Plural transponders are provided in the communication satellite to relay and transmit the broadcasting data of plural transmission channels to the earth.
By the way, in a cable television system for distributing information such as television programs or the like by a cable (hereinafter, this is referred to as CATV (cable television)), a repeater system which receives a digital multiplex satellite broadcasting wave distributed via a communication satellite and redistributes this as a cable television program broadcasting is considered.
As one of methods for receiving and distributing a digital multiplex satellite broadcasting wave to a CATV, a method for demodulating a signal relayed by one of the single transponders of a communication satellite to generate a transport stream, and then modulating the above transport stream correspondingly to the CATV, and transmitting this to a single CATV channel is considered. In the case of this method, as shown in FIG. 1, all program channels included in the transmission channel relayed by the specified transponder are distributed to the single CATV channel. For example, in the case where a transponder Tr1 of satellite broadcasting corresponds to a CATV channel Ch1 of CATV, program channels C1, C2 and C3 which have been multiplexed in a transmission channel to be distributed by relayed by the transponder Tr1 are multiplexed into the CATV channel Ch1.
In the case where a digital multiplex satellite broadcasting is redistributed to a CATV by the above method, however, since a transmission channel to be relayed to a single CATV channel by a single transponder is distributed, it is difficult to selectively distribute a program channel to be relayed by another transponder to the above CATV channel. Thus, a desired program channel cannot be distributed to a single CATV channel from among plural transmission channels, and it causes a problem in usability.
The present invention has been done considering the above point and is proposing an information repeater system capable of selecting and distributing a desired broadcasting program with a simple construction.
In view of the foregoing, an object of this invention is to provide an information repeater system for receiving a broadcasting wave formed by multiplexing plural broadcastings and distributing it to the corresponding channel of a specified broadcasting system, in which a data stream relayed by a specified transponder is extracted from the broadcasting wave, an arbitrary packet is specified and extracted from the above data stream, and the above extracted packet is transmitted to the specified channel of the specified broadcasting system. Thereby, a desired channel can be extracted and transmitted to the desired channel of the specified broadcasting system from among the plural broadcastings multiplexed in the broadcasting wave.
The data stream relayed by the specified transponder is extracted from the broadcasting wave, and thus extracted data stream is assigned to a specified packet extracting means. In the above packet extracting means, the arbitrary packet is specified and extracted from the data stream, and thus-extracted packet is transmitted to the specified channel of the specified broadcasting system. Thereby, the desired channel can be extracted from the plural broadcastings multiplexed in the broadcasting wave and can be transmitted to the desired channel of the specified broadcasting system.
Furthermore, since a single packet extracting means is made to correspond to each broadcasting program to be distributed to the specified broadcasting system, the number of the above packet extracting means can be limited to the number of broadcastings to be distributed. Thus, the constitution of the information repeater system can be simplified.
This repeater system has a system information update detecting means for detecting whether or not the contents of system information to make the desired program channel correspond to a packet corresponding to said desired program channel has been updated. Thereby, if it is detected that the contents of said system information has been updated by said update detecting means, the system information is replaced by new system information in a system information memory means.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.